1. Field of the Invention
The present invention relates generally to hand tools and hand instruments. It relates in particular to hand held tools and hand held instruments which provide illumination of the site upon which the tool or instrument operates to bring about a desired effect.
2. Description of the Related Art
Hand held tools (e.g., implements used in carpentry, metal working, plumbing, and electricity) and hand held instruments (e.g., implements used in medicine, surgery, dentistry, drawing, painting, sculpting, crocheting, and knitting) have been known and employed for many, many years. However, in recent times attempts have been made to provide certain of these tools and instruments with an internal source of illumination, so that the area being worked on by the tool or instrument can be lighted without the employment of an outside illuminating source. For example, U.S. Pat. Nos. 2,378,544 and 2,344,370 disclose hand held knitting needles which provide some illumination of the workpiece. However, in both cases illumination is provided through the knitting needle itself. This does not afford enough light, and the light which is afforded is a small spot located at the exact point of contact with the workpiece. Moreover, the Lucite needles and phosphorescent tips of these references are brittle, scratch easily, and therefore have a limited useful life. Furthermore, one of these devices requires house current and has no effective on-off switch. As additional examples, U.S. Pat. Nos. 4,107,765 and 4,283,757 disclose hand tools such as screwdrivers which also provide for some illumination of the workpiece. However, these devices are also found wanting, because: they provide a spotty, rather than a concentric, evenly-illuminated working site; they do not disclose an on-off switch which operates simply, facilely, and positively, having no working parts to wear out; and they do not comprehend the interchangeability of various types of working implements.